draft-ietf-pce-hierarchy-extensions-11.txt   rfc8685.txt 
PCE Working Group F. Zhang Internet Engineering Task Force (IETF) F. Zhang
Internet-Draft Q. Zhao Request for Comments: 8685 Q. Zhao
Intended status: Standards Track Huawei Category: Standards Track Huawei
Expires: December 2, 2019 O. Gonzalez de Dios ISSN: 2070-1721 O. Gonzalez de Dios
Telefonica I+D Telefonica I+D
R. Casellas R. Casellas
CTTC CTTC
D. King D. King
Old Dog Consulting Old Dog Consulting
June 1, 2019 December 2019
Extensions to Path Computation Element Communication Protocol (PCEP) for Path Computation Element Communication Protocol (PCEP) Extensions
Hierarchical Path Computation Elements (PCE) for the Hierarchical Path Computation Element (H-PCE) Architecture
draft-ietf-pce-hierarchy-extensions-11
Abstract Abstract
The Hierarchical Path Computation Element (H-PCE) architecture is The Hierarchical Path Computation Element (H-PCE) architecture is
defined in RFC 6805. It provides a mechanism to derive an optimum defined in RFC 6805. It provides a mechanism to derive an optimum
end-to-end path in a multi-domain environment by using a hierarchical end-to-end path in a multi-domain environment by using a hierarchical
relationship between domains to select the optimum sequence of relationship between domains to select the optimum sequence of
domains and optimum paths across those domains. domains and optimum paths across those domains.
This document defines extensions to the Path Computation Element This document defines extensions to the Path Computation Element
Protocol (PCEP) to support Hierarchical PCE procedures. Communication Protocol (PCEP) to support H-PCE procedures.
Status of This Memo Status of This Memo
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . .3 1. Introduction
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . .4 1.1. Scope
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . .5 1.2. Terminology
1.3. Requirements Language . . . . . . . . . . . . . . . . . .5 1.3. Requirements Language
2. Requirements for H-PCE . . . . . . . . . . . . . . . . . . .5 2. Requirements for the H-PCE Architecture
2.1. Path Computation Request . . . . . . . . . . . . . . . .6 2.1. Path Computation Requests
2.1.1. Qualification of PCEP Requests . . . . . . . . . . .6 2.1.1. Qualification of PCEP Requests
2.1.2. Multi-domain Objective Functions . . . . . . . . . .6 2.1.2. Multi-domain Objective Functions
2.1.3. Multi-domain Metrics . . . . . . . . . . . . . . . .7 2.1.3. Multi-domain Metrics
2.2. Parent PCE Capability Advertisement . . . . . . . . . . .7 2.2. Parent PCE Capability Advertisement
2.3. PCE Domain Identification . . . . . . . . . . . . . . . .7 2.3. PCE Domain Identification
2.4. Domain Diversity . . . . . . . . . . . . . . . . . . . .7 2.4. Domain Diversity
3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . .8 3. PCEP Extensions
3.1 Applicability to PCC-PCE Communications . . . . . . . . .8 3.1. Applicability to PCC-PCE Communications
3.2. OPEN Object . . . . . . . . . . . . . . . . . . . . . . .8 3.2. OPEN Object
3.2.1. H-PCE Capability TLV . . . . . . . . . . . . . . . .8 3.2.1. H-PCE-CAPABILITY TLV
3.2.1.1 Backwards Compatibility . . . . . . . . . . . . . . .9 3.2.1.1. Backwards Compatibility
3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . .10 3.2.2. Domain-ID TLV
3.3. RP Object . . . . . . . . . . . . . . . . . . . . . . . .11 3.3. RP Object
3.3.1. H-PCE-FLAG TLV . . . . . . . . . . . . . . . . . . .11 3.3.1. H-PCE-FLAG TLV
3.3.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . .12 3.3.2. Domain-ID TLV
3.4. Objective Functions . . . . . . . . . . . . . . . . . . .12 3.4. Objective Functions
3.4.1. OF Codes . . . . . . . . . . . . . . . . . . . . . .12 3.4.1. OF Codes
3.4.2. OF Object . . . . . . . . . . . . . . . . . . . . . .13 3.4.2. OF Object
3.5. Metric Object . . . . . . . . . . . . . . . . . . . . . .14 3.5. METRIC Object
3.6. SVEC Object . . . . . . . . . . . . . . . . . . . . . . .15 3.6. SVEC Object
3.7. PCEP-ERROR Object . . . . . . . . . . . . . . . . . . . .15 3.7. PCEP-ERROR Object
3.7.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . .15 3.7.1. Hierarchical PCE Error-Type
3.8. NO-PATH Object . . . . . . . . . . . . . . . . . . . . .16 3.8. NO-PATH Object
4. H-PCE Procedures . . . . . . . . . . . . . . . . . . . . . .16 4. H-PCE Procedures
4.1. OPEN Procedure between Child PCE and Parent PCE . . . . .16 4.1. OPEN Procedure between Child PCE and Parent PCE
4.2. Procedure to Obtain Domain Sequence . . . . . . . . . . .17 4.2. Procedure for Obtaining the Domain Sequence
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . .17 5. Error Handling
6. Manageability Considerations . . . . . . . . . . . . . . . .18 6. Manageability Considerations
6.1. Control of Function and Policy . . . . . . . . . . . . .18 6.1. Control of Function and Policy
6.1.1. Child PCE . . . . . . . . . . . . . . . . . . . . . .18 6.1.1. Child PCE
6.1.2. Parent PCE . . . . . . . . . . . . . . . . . . . . . 6.1.2. Parent PCE
6.1.3. Policy Control
6.1.3. Policy Control . . . . . . . . . . . . . . . . . . .19 6.2. Information and Data Models
6.2. Information and Data Models . . . . . . . . . . . . . . .19 6.3. Liveness Detection and Monitoring
6.3. Liveness Detection and Monitoring . . . . . . . . . . . .20 6.4. Verifying Correct Operations
6.4. Verify Correct Operations . . . . . . . . . . . . . . . .20 6.5. Requirements on Other Protocols
6.5. Requirements On Other Protocols . . . . . . . . . . . . .20 6.6. Impact on Network Operations
6.6. Impact On Network Operations . . . . . . . . . . . . . .20 7. IANA Considerations
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . .20 7.1. PCEP TLV Type Indicators
7.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . .20 7.2. H-PCE-CAPABILITY TLV Flags
7.2. H-PCE-CAPABILITY TLV Flags . . . . . . . . . . . . . . .21 7.3. Domain-ID TLV Domain Type
7.3. Domain-ID TLV Domain type . . . . . . . . . . . . . . . .21 7.4. H-PCE-FLAG TLV Flags
7.4. H-PCE-FLAG TLV Flags . . . . . . . . . . . . . . . . . .22 7.5. OF Codes
7.5. OF Codes . . . . . . . . . . . . . . . . . . . . . . . .22 7.6. METRIC Object Types
7.6. METRIC Types . . . . . . . . . . . . . . . . . . . . . .22 7.7. New PCEP Error-Types and Values
7.7. New PCEP Error-Types and Values . . . . . . . . . . . . .23 7.8. New NO-PATH-VECTOR TLV Bit Flag
7.8. New NO-PATH-VECTOR TLV Bit Flag . . . . . . . . . . . . .23 7.9. SVEC Flag
7.9. SVEC Flag . . . . . . . . . . . . . . . . . . . . . . . .24 8. Security Considerations
7.10. NO-PATH VECTOR TLV Bit Flag. . . . . . . . . . . . . . .24 9. References
8. Security Considerations . . . . . . . . . . . . . . . . . . .24 9.1. Normative References
9. Contributing Authors . . . . . . . . . . . . . . . . . . . . .24 9.2. Informative References
10.Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .25 Acknowledgements
11. References . . . . . . . . . . . . . . . . . . . . . . . . .25 Contributors
11.1. Normative References . . . . . . . . . . . . . . . . . .25 Authors' Addresses
11.2. Informative References . . . . . . . . . . . . . . . . .25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .28
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
A1. Implementation Status . . . . . . . . . . . . . . . . . . .28
A1.1. Inter-layer traffic engineering with H-PCE . . . . . . .29
A1.2. Telefonica Netphony (Open Source PCE) . . . . . . . . .30
A1.3. H-PCE Proof of Concept developed by Huawei . . . . . . .31
1. Introduction 1. Introduction
The Path Computation Element communication Protocol (PCEP) provides The Path Computation Element Communication Protocol (PCEP) provides a
a mechanism for Path Computation Elements (PCEs) and Path Computation mechanism for Path Computation Elements (PCEs) and Path Computation
Clients (PCCs) to exchange requests for path computation and Clients (PCCs) to exchange requests for path computation and
responses that provide computed paths. responses that provide computed paths.
The capability to compute the routes of end-to-end inter-domain MPLS The capability to compute the routes of end-to-end inter-domain MPLS
Traffic Engineering (MPLS-TE) and GMPLS Label Switched Paths (LSPs) Traffic Engineering (MPLS-TE) and GMPLS Label Switched Paths (LSPs)
is expressed as requirements in [RFC4105] and [RFC4216]. This is expressed as requirements in [RFC4105] and [RFC4216]. This
capability may be realized by a PCE [RFC4655]. The methods for capability may be realized by a PCE [RFC4655]. The methods for
establishing and controlling inter-domain MPLS-TE and GMPLS LSPs are establishing and controlling inter-domain MPLS-TE and GMPLS LSPs are
documented in [RFC4726]. documented in [RFC4726].
[RFC6805] describes a Hierarchical PCE (H-PCE) architecture which can [RFC6805] describes a Hierarchical Path Computation Element (H-PCE)
be used for computing end-to-end paths for inter-domain MPLS Traffic architecture that can be used for computing end-to-end paths for
Engineering (TE) and GMPLS Label Switched Paths (LSPs). inter-domain MPLS-TE and GMPLS LSPs.
Within the hierarchical PCE architecture, the parent PCE is used to In the H-PCE architecture, the parent PCE is used to compute a multi-
compute a multi-domain path based on the domain connectivity domain path based on the domain connectivity information. A child
information. A child PCE may be responsible for single or multiple PCE may be responsible for single or multiple domains and is used to
domains and is used to compute the intra-domain path based on its compute the intra-domain path based on its own domain topology
own domain topology information. information.
The H-PCE end-to-end domain path computation procedure is described The H-PCE end-to-end domain path computation procedure is described
below: below:
o A path computation client (PCC) sends the inter-domain path * A PCC sends the inter-domain Path Computation Request (PCReq)
computation requests to the child PCE responsible for its domain; messages [RFC5440] to the child PCE responsible for its domain.
o The child PCE forwards the request to the parent PCE; * The child PCE forwards the request to the parent PCE.
o The parent PCE computes the likely domain paths from the ingress * The parent PCE computes the likely domain paths from the ingress
domain to the egress domain; domain to the egress domain.
o The parent PCE sends the intra-domain path computation requests * The parent PCE sends the intra-domain PCReq messages (between the
(between the domain border nodes) to the child PCEs which are domain border nodes) to the child PCEs that are responsible for
responsible for the domains along the domain path; the domains along the domain path.
o The child PCEs return the intra-domain paths to the parent PCE; * The child PCEs return the intra-domain paths to the parent PCE.
o The parent PCE constructs the end-to-end inter-domain path based * The parent PCE constructs the end-to-end inter-domain path based
on the intra-domain paths; on the intra-domain paths.
o The parent PCE returns the inter-domain path to the child PCE; * The parent PCE returns the inter-domain path to the child PCE.
o The child PCE forwards the inter-domain path to the PCC. * The child PCE forwards the inter-domain path to the PCC.
The parent PCE may be requested to provide only the sequence of The parent PCE may be requested to provide only the sequence of
domains to a child PCE so that alternative inter-domain path domains to a child PCE so that alternative inter-domain path
computation procedures, including Per Domain (PD) [RFC5152] and computation procedures, including per-domain (PD) path computation
Backwards Recursive Path Computation (BRPC) [RFC5441], may be used. [RFC5152] and Backward-Recursive PCE-Based Computation (BRPC)
[RFC5441], may be used.
This document defines the PCEP extensions for the purpose of This document defines the PCEP extensions for the purpose of
implementing Hierarchical PCE procedures, which are described in implementing H-PCE procedures, which are described in [RFC6805].
[RFC6805].
1.1. Scope 1.1. Scope
The following functions are out of scope of this document: The following functions are out of scope for this document:
o Determination of Destination Domain (section 4.5 of [RFC6805]): * Determination of the destination domain (Section 4.5 of
[RFC6805]):
* via a collection of reachability information from child domain; - via a collection of reachability information from child
domains,
* via requests to the child PCEs to discover if they contain the - via requests to the child PCEs to discover if they contain the
destination node; destination node, or
* or any other methods. - via any other methods.
o Parent Traffic Engineering Database (TED) methods (section 4.4 of * Parent Traffic Engineering Database (TED) methods (Section 4.4 of
[RFC6805]), although suitable mechanisms include: [RFC6805]), although suitable mechanisms include:
* YANG-based management interfaces; - YANG-based management interfaces.
* BGP-LS [RFC7752]; - BGP - Link State (BGP-LS) [RFC7752].
* Future extension to PCEP (such as [I-D.dhodylee-pce-pcep-ls]). - Future extensions to PCEP (for example, see [PCEP-LS]).
o Learning of Domain connectivity and boundary nodes (BN) addresses, * Learning of domain connectivity and border node addresses.
methods to achieve this function include: Methods to achieve this function include:
* YANG-based management interfaces; - YANG-based management interfaces.
* BGP-LS [RFC7752]; - BGP-LS [RFC7752].
* Future extension to PCEP (such as [I-D.dhodylee-pce-pcep-ls]). - Future extensions to PCEP (for example, see [PCEP-LS]).
o Stateful PCE Operations (Refer [I-D.ietf-pce-stateful-hpce]) * Stateful PCE operations. (Refer to [STATEFUL-HPCE].)
o Applicability of hierarchical PCE to large multi-domain * Applicability of the H-PCE model to large multi-domain
environments. environments.
* The hierarchical relationship model is described in [RFC6805]. - The hierarchical relationship model is described in [RFC6805].
It is applicable to environments with small groups of domains It is applicable to environments with small groups of domains
where visibility from the ingress LSRs is limited. As highlighted where visibility from the ingress Label Switching Routers
in [RFC7399] applying the hierarchical PCE model to very large (LSRs) is limited. As highlighted in [RFC7399], applying the
groups of domains, such as the Internet, is not considered H-PCE model to very large groups of domains, such as the
feasible or desirable. Internet, is not considered feasible or desirable.
1.2. Terminology 1.2. Terminology
This document uses the terminology defined in [RFC4655], [RFC5440] This document uses the terminology defined in [RFC4655] and
and the additional terms defined in Section 1.4 of [RFC6805]. [RFC5440], and the additional terms defined in Section 1.4 of
[RFC6805].
1.3. Requirements Language 1.3. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Requirements for H-PCE 2. Requirements for the H-PCE Architecture
This section compiles the set of requirements to the PCEP extensions
to support the H-PCE architecture and procedures.
[RFC6805] identifies high-level requirements of PCEP extensions
required to support the hierarchical PCE model.
2.1. Path Computation Request This section compiles the set of requirements for the PCEP extensions
to support the H-PCE architecture and procedures. [RFC6805]
identifies high-level requirements for PCEP extensions that are
required for supporting the H-PCE model.
The Path Computation Request (PCReq) [RFC5440] messages are used by 2.1. Path Computation Requests
a PCC or a PCE to make a path computation request to a PCE. In order
to achieve the full functionality of the H-PCE procedures, the PCReq
message needs to include:
o Qualification of PCE Requests (Section 4.8.1. of [RFC6805]); The PCReq messages [RFC5440] are used by a PCC or a PCE to make a
path computation request to a PCE. In order to achieve the full
functionality of the H-PCE procedures, the PCReq message needs to
include:
o Multi-domain Objective Functions (OF); * Qualification of PCE requests (Section 4.8.1 of [RFC6805]).
o Multi-domain Metrics. * Multi-domain Objective Functions (OFs).
* Multi-domain metrics.
2.1.1. Qualification of PCEP Requests 2.1.1. Qualification of PCEP Requests
As described in Section 4.8.1 of [RFC6805], the H-PCE architecture As described in Section 4.8.1 of [RFC6805], the H-PCE architecture
introduces new request qualifications, which are: introduces new request qualifications, which are as follows:
o The ability for a child PCE to indicate that a path computation * The ability for a child PCE to indicate that a PCReq message sent
request sent to a parent PCE should be satisfied by a domain to a parent PCE should be satisfied by a domain sequence only --
sequence only, that is, not by a full end-to-end path. This allows that is, not by a full end-to-end path. This allows the child PCE
the child PCE to initiate a per-domain (PD) [RFC5152] or a to initiate a PD path computation per [RFC5152] or a BRPC
backward recursive path computation (BRPC) [RFC5441]. procedure [RFC5441].
o As stated in [RFC6805], Section 4.5, if a PCC knows the egress * As stated in [RFC6805], Section 4.5, if a PCC knows the egress
domain, it can supply this information as the path computation domain, it can supply this information as part of the PCReq
request. The PCC may also want to specify the destination domain message. The PCC may also want to specify the destination domain
information in a PCEP request, if it is known. information in a PCEP request, if it is known.
o An inter domain path computed by parent PCE should be capable of * An inter-domain path computed by a parent PCE should be capable of
disallowing specific domain re-entry. disallowing re-entry into a specified domain.
2.1.2. Multi-domain Objective Functions 2.1.2. Multi-domain Objective Functions
For H-PCE inter-domain path computation, there are three new For H-PCE inter-domain path computation, there are three new OFs
Objective Functions defined in this document: defined in this document:
o Minimize the number of Transit Domains (MTD) * Minimize the number of Transit Domains (MTD)
o Minimize the number of border nodes (MBN)
o Minimize the number of Common Transit Domains (MCTD)
The PCC may specify the multi-domain Objective Function code to * Minimize the number of Border Nodes (MBN)
use when requesting inter-domain path computation, it may also
include intra-domain OFs, such as Minimum Cost Path (MCP) [RFC5441], * Minimize the number of Common Transit Domains (MCTD)
which must be considered by participating child PCEs.
The PCC may specify the multi-domain OF code to use when requesting
inter-domain path computation. It may also include intra-domain OFs,
such as Minimum Cost Path (MCP) [RFC5541], which must be considered
by participating child PCEs.
2.1.3. Multi-domain Metrics 2.1.3. Multi-domain Metrics
For inter-domain path computation, there are several path metrics of For inter-domain path computation, there are two path metrics of
interest. interest.
o Domain count (number of domains crossed); * Domain Count (number of domains crossed).
o Border Node count. * Border Node Count.
A PCC may be able to limit the number of domains crossed by applying A PCC may be able to limit the number of domains crossed by applying
a limit on these metrics. Details in Section 3.4. a limit on these metrics. See Section 3.4 for details.
2.2. Parent PCE Capability Advertisement 2.2. Parent PCE Capability Advertisement
A PCEP Speaker (Parent PCE or Child PCE) that supports and wishes A PCEP speaker (parent PCE or child PCE) that supports and wishes to
to use the procedures described in this document must advertise use the procedures described in this document must advertise this
the fact and negotiate its role with its PCEP peers. It does this fact and negotiate its role with its PCEP peers. It does this using
using the "H-PCE Capability" TLV, described in Section 3.2.1, in the the "H-PCE Capability" TLV, as described in Section 3.2.1, in the
OPEN Object to advertise its support for PCEP extensions for H-PCE OPEN object [RFC5440] to advertise its support for PCEP extensions
Capability. for the H-PCE capability.
During the PCEP session establishment procedure, the child PCE needs During the PCEP session establishment procedure, the child PCE needs
to be capable of indicating to the parent PCE whether it requests the to be capable of indicating to the parent PCE whether it requests the
parent PCE capability or not. parent PCE capability or not.
2.3. PCE Domain Identification 2.3. PCE Domain Identification
A PCE domain is a single domain with an associated PCE. Although it A PCE domain is a single domain with an associated PCE, although it
is possible for a PCE to manage multiple domains simultaneously. The is possible for a PCE to manage multiple domains simultaneously. The
PCE domain could be an IGP area or AS. PCE domain could be an IGP area or Autonomous System (AS).
The PCE domain identifiers MAY be provided during the PCEP session The PCE domain identifiers MAY be provided during the PCEP session
establishment procedure. establishment procedure.
2.4. Domain Diversity 2.4. Domain Diversity
In a multi-domain environment, Domain Diversity is defined in "Domain diversity" in the context of a multi-domain environment is
[RFC6805] and described as "A pair of paths are domain-diverse if defined in [RFC6805] and described as follows:
they do not transit any of the same domains. A pair of paths that
share a common ingress and egress are domain-diverse if they only | A pair of paths are domain-diverse if they do not transit any of
share the same domains at the ingress and egress (the ingress and | the same domains. A pair of paths that share a common ingress and
egress domains). Domain diversity may be maximized for a pair of | egress are domain-diverse if they only share the same domains at
paths by selecting paths that have the smallest number of shared | the ingress and egress (the ingress and egress domains). Domain
domains." | diversity may be maximized for a pair of paths by selecting paths
The main motivation behind domain diversity is to avoid fate sharing, | that have the smallest number of shared domains.
but it can also be because of some geo-political reasons and
commercial relationships that would require domain diversity. For The main motivation behind domain diversity is to avoid fate-sharing.
example, a pair of paths should choose different transit Autonomous However, domain diversity may also be requested to avoid specific
System (AS) because of some policy considerations. transit domains due to security, geopolitical, and commercial
reasons. For example, a pair of paths should choose different
transit ASes because of certain policy considerations.
In the case when full domain diversity could not be achieved, it is In the case when full domain diversity could not be achieved, it is
helpful to minimize the commonly shared domains. Also, it is helpful to minimize the commonly shared domains. Also, it is
interesting to note that other scope of diversity (node, link, SRLG interesting to note that other domain-diversity techniques (node,
etc.) can still be applied inside the commonly shared domains. link, Shared Risk Link Group (SRLG), etc.) can still be applied
inside the commonly shared domains.
3. PCEP Extensions 3. PCEP Extensions
This section defines extensions to PCEP [RFC5440] to support the This section defines extensions to PCEP [RFC5440] to support the
H-PCE procedures. H-PCE procedures.
3.1 Applicability to PCC-PCE Communications 3.1. Applicability to PCC-PCE Communications
Although the extensions defined in this document are intended Although the extensions defined in this document are intended
primarily for use between a child PCE and a parent PCE, they are primarily for use between a child PCE and a parent PCE, they are also
also applicable for communications between a PCC and its PCE. applicable for communications between a PCC and its PCE.
Thus, the information that may be encoded in a PCReq can be sent Thus, the information that may be encoded in a PCReq can be sent from
from a PCC towards the child PCE. This includes the RP object a PCC towards the child PCE. This includes the Request Parameters
(Section 3.3) and the Objective Function (OF) codes and objects (RP) object ([RFC5440] and Section 3.3), the OF codes
(Section 3.4). A PCC and a child PCE could also exchange the (Section 3.4.1), and the OF object (Section 3.4.2). A PCC and a
capability (Section 3.2.1) during its session. child PCE could also exchange the H-PCE capability (Section 3.2.1)
during its session.
This allows a PCC to request paths that transit multiple This allows a PCC to request paths that transit multiple domains
domains utilizing the capabilities defined in this document. utilizing the capabilities defined in this document.
3.2. OPEN Object 3.2. OPEN Object
Two new TLVs are defined in this document to be carried within an This document defines two new TLVs to be carried in an OPEN object.
OPEN object. This way, during the PCEP session establishment, the This way, during the PCEP session establishment, the H-PCE capability
H-PCE capability and Domain information can be advertised. and domain information can be advertised.
3.2.1. H-PCE Capability TLV 3.2.1. H-PCE-CAPABILITY TLV
The H-PCE-CAPABILITY TLV is an optional TLV associated with the OPEN The H-PCE-CAPABILITY TLV is an optional TLV associated with the OPEN
Object [RFC5440] to exchange H-PCE capability of PCEP speakers. object [RFC5440] to exchange the H-PCE capability of PCEP speakers.
Its format is shown in the following figure: Its format is shown in the following figure:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type= TBD1 | Length=4 | | Type=13 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |P| | Flags |P|
+---------------------------------------------------------------+ +---------------------------------------------------------------+
Figure 1: H-PCE-CAPABILITY TLV format Figure 1: H-PCE-CAPABILITY TLV Format
The type of the TLV is TBD1 (to be assigned by IANA), and it has a The type of the TLV is 13, and it has a fixed length of 4 octets.
fixed length of 4 octets.
The value comprises a single field - Flags (32 bits): The value comprises a single field -- Flags (32 bits):
P (Parent PCE Request bit): if set, will signal that the child PCE P (Parent PCE Request bit):
wishes to use the peer PCE as a parent PCE. If set, will signal that the child PCE wishes to use the peer
PCE as a parent PCE.
Unassigned bits MUST be set to 0 on transmission and MUST be ignored Unassigned bits MUST be set to 0 on transmission and MUST be ignored
on receipt. on receipt.
The inclusion of this TLV in an OPEN object indicates that the H-PCE The inclusion of this TLV in an OPEN object indicates that the H-PCE
extensions are supported by the PCEP speaker. The child PCE MUST extensions are supported by the PCEP speaker. The child PCE MUST
include this TLV and set the P flag. The parent PCE MUST include include this TLV and set the P-flag. The parent PCE MUST include
this TLV and unset the P flag. this TLV and unset the P-flag.
The setting of the P flag (parent PCE request bit) would mean that The setting of the P-flag (Parent PCE Request bit) would mean that
the PCEP speaker wants the peer to be a parent PCE, so in the case the PCEP speaker wants the peer to be a parent PCE, so in the case of
of a PCC to Child-PCE relationship, neither entity would set the P a PCC-to-child-PCE relationship, neither entity would set the P-flag.
flag.
If both peers attempt to set the P flag then the session If both peers attempt to set the P-flag, then the session
establishment MUST fail, and the PCEP speaker MUST respond with PCErr establishment MUST fail, and the PCEP speaker MUST respond with a
message using Error-Type 1: "PCEP Session Establishment Failure" as PCErr message using Error-Type 1 (PCEP session establishment failure)
per [RFC5440]. as per [RFC5440].
If the PCE understands the H-PCE path computation request but did not If the PCE understands the H-PCE PCReq message but did not advertise
advertise its H-PCE capability, it MUST send a PCErr message with its H-PCE capability, it MUST send a PCErr message with Error-Type=28
Error-Type=TBD8 ("H-PCE error") and Error-Value=1 ("H-PCE Capability (H-PCE Error) and Error-Value=1 (H-PCE Capability not advertised).
not advertised").
3.2.1.1 Backwards Compatibility 3.2.1.1. Backwards Compatibility
Section 7.1 of [RFC5440] requires that "Unrecognized TLVs MUST be Section 7.1 of [RFC5440] specifies the following requirement:
ignored. "Unrecognized TLVs MUST be ignored."
That means that a PCE that does not support this document but that The OPEN object [RFC5440] contains the necessary PCEP information
receives an Open Message containing an Open Object that includes between the PCE entities, including session information and PCE
an H-PCE-CAPABILITIES TLV will ignore that TLV and will continue to capabilities via TLVs (including if H-PCE is supported). If the PCE
attempt to establish a PCEP session. It will, however, not include does not support this document but receives an Open message
the TLV in the Open message that it sends, so the H-PCE relationship containing an OPEN object that includes an H-PCE-CAPABILITY TLV, it
will not be created. will ignore that TLV and continue to attempt to establish a PCEP
session. However, it will not include the TLV in the Open message
that it sends, so the H-PCE relationship will not be created.
If a PCE does not support the extensions defined in this document but If a PCE does not support the extensions defined in this document but
receives them in a PCEP message (notwithstanding the fact that the receives them in a PCEP message (notwithstanding the fact that the
session was not established as supporting a H-PCE relationship), the session was not established as supporting an H-PCE relationship), the
receiving PCE will ignore the H-PCE related parameters because they receiving PCE will ignore the H-PCE related parameters because they
are all encoded in TLVs within standard PCEP objects. are all encoded in TLVs in standard PCEP objects.
3.2.2. Domain-ID TLV 3.2.2. Domain-ID TLV
The Domain-ID TLV, when used in the OPEN object, identifies the The Domain-ID TLV, when used in the OPEN object, identifies the
domains served by the PCE. The child PCE uses this mechanism to domains served by the PCE. The child PCE uses this mechanism to
inform the domain information to the parent PCE. provide the domain information to the parent PCE.
The Domain-ID TLV is defined below: The Domain-ID TLV is defined below:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type= TBD2 | Length | | Type=14 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain Type | Reserved | | Domain Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
// Domain ID // // Domain ID //
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Domain-ID TLV format Figure 2: Domain-ID TLV Format
The type of the TLV is TBD2 (to be assigned by IANA), and it has a The type of the TLV is 14, and it has a variable Length of the value
variable Length of the value portion. The value part comprises: portion. The value part comprises the following:
Domain Type (8 bits): Indicates the domain type. Four types of Domain Type (8 bits): Indicates the domain type. Four types of
domain are currently defined: domains are currently defined:
* Type=1: the Domain ID field carries a 2-byte AS number. Padded Type=1: The Domain ID field carries a 2-byte AS number.
with trailing zeros to a 4-byte boundary. Padded with trailing zeros to a 4-byte boundary.
* Type=2: the Domain ID field carries a 4-byte AS number. Type=2: The Domain ID field carries a 4-byte AS number.
* Type=3: the Domain ID field carries a 4-byte OSPF area ID. Type=3: The Domain ID field carries a 4-byte OSPF area ID.
* Type=4: the Domain ID field carries (2-byte Area-Len, variable Type=4: The Domain ID field carries a 2-byte Area-Len and a
length IS-IS area ID). Padded with trailing zeros to a 4-byte variable-length IS-IS area ID. Padded with trailing
boundary. zeros to a 4-byte boundary.
Reserved: Zero at transmission; ignored at the receipt. Reserved: Zero at transmission; ignored on receipt.
Domain ID (variable): Indicates an IGP Area ID or AS number as Domain ID (variable): Indicates an IGP area ID or AS number as
per the Domain Type field. It can be 2 bytes, 4 bytes or variable per the Domain Type field. It can be 2 bytes, 4 bytes, or
length depending on the domain identifier used. It is padded with variable length, depending on the domain identifier used. It
trailing zeros to a 4-byte boundary. In case of IS-IS it includes is padded with trailing zeros to a 4-byte boundary. In the
the Area-Len as well. case of IS-IS, it includes the Area-Len as well.
In the case a PCE serves more than one domain, multiple Domain-ID In the case where a PCE serves more than one domain, multiple Domain-
TLVs are included for each domain it serves. ID TLVs are included for each domain it serves.
3.3. RP Object 3.3. RP Object
3.3.1. H-PCE-FLAG TLV 3.3.1. H-PCE-FLAG TLV
The H-PCE-FLAG TLV is an optional TLV associated with the RP Object The H-PCE-FLAG TLV is an optional TLV associated with the RP object
[RFC5440] to indicate the H-PCE path computation request and options. [RFC5440] to indicate the H-PCE PCReq message and options.
Its format is shown in the following figure: Its format is shown in the following figure:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type= TBD3 | Length=4 | | Type=15 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |D|S| | Flags |D|S|
+---------------------------------------------------------------+ +---------------------------------------------------------------+
Figure 3: H-PCE-FLAG TLV format Figure 3: H-PCE-FLAG TLV Format
The type of the TLV is TBD3 (to be assigned by IANA), and it has a The type of the TLV is 15, and it has a fixed length of 4 octets.
fixed length of 4 octets.
The value comprises a single field - Flags (32 bits): The value comprises a single field -- Flags (32 bits):
S (Domain Sequence bit): if set, will signal that the child PCE D (Disallow Domain Re-entry bit):
wishes to get only the domain sequence in the path computation If set, will signal that the computed path does not enter a
reply. Refer to Section 3.7 of [RFC7897] for details. domain more than once.
D (Disallow Domain Re-entry bit): if set, will signal that the S (Domain Sequence bit):
computed path does not enter a domain more than once. If set, will signal that the child PCE wishes to get only the
domain sequence in the Path Computation Reply (PCRep) message
[RFC5440]. Refer to Section 3.7 of [RFC7897] for details.
Unassigned bits MUST be set to 0 on transmission and MUST be ignored Unassigned bits MUST be set to 0 on transmission and MUST be ignored
on receipt. on receipt.
The presence of the TLV indicates that the H-PCE based path The presence of the TLV indicates that the H-PCE-based path
computation is requested as per this document. computation is requested as per this document.
3.3.2. Domain-ID TLV 3.3.2. Domain-ID TLV
The Domain-ID TLV, carried in an OPEN object, is used to indicate a The Domain-ID TLV, carried in an OPEN object, is used to indicate a
(list of) managed domains and is described in Section 3.3.1. This managed domain (or a list of managed domains) and is described in
TLV, when carried in an RP object, indicates the destination domain Section 3.2.2. This TLV, when carried in an RP object, indicates the
ID. If a PCC knows the egress domain, it can supply this information destination domain ID. If a PCC knows the egress domain, it can
in the PCReq message. The format and procedure of this TLV are supply this information in the PCReq message. Section 3.2.2 also
defined in Section 3.2.2. defines the format for this TLV and the procedure for using it.
If a Domain-id TLV is used in the RP object, and the destination is If a Domain-ID TLV is used in the RP object and the destination is
not actually in the indicated domain, then the parent not actually in the indicated domain, then the parent PCE should
PCE should respond with a NO-PATH object and NO-PATH VECTOR TLV respond with a NO-PATH object and the NO-PATH-VECTOR TLV should be
should be used. A new bit number is assigned to indicate used. A new bit number is assigned to indicate "Destination is not
"Destination not found in the indicated domain" (see Section 3.7). found in the indicated domain" (see Section 3.8).
3.4. Objective Functions 3.4. Objective Functions
3.4.1. OF Codes 3.4.1. OF Codes
[RFC5541] defines a mechanism to specify an Objective Function that [RFC5541] defines a mechanism to specify an OF that is used by a PCE
is used by a PCE when it computes a path. Three new Objective when it computes a path. Three new OFs are defined for the H-PCE
Functions are defined for H-PCE, these are: model; these are:
o MTD * MTD
* Name: Minimize the number of Transit Domains (MTD) Name: Minimize the number of Transit Domains (MTD)
* Objective Function Code - TBD4 (to be assigned by IANA) OF code: 12
* Description: Find a path P such that it passes through the Description: Find a path P such that it passes through the least
least number of transit domains. number of transit domains.
* Objective functions are formulated using the following - OFs are formulated using the following terminology:
terminology:
+ A network comprises a set of N domains {Di, (i=1...N)}. o A network comprises a set of N domains {Di, (i=1...N)}.
+ A path P passes through K unique domains {Dpi,(i=1...K)}. o A path P passes through K unique domains {Dpi, (i=1...K)}.
+ Find a path P such that the value of K is minimized. o Find a path P such that the value of K is minimized.
o MBN * MBN
* Name: Minimize the number of border nodes. Name: Minimize the number of Border Nodes (MBN)
* Objective Function Code - TBD5 (to be assigned by IANA) OF code: 13
* Description: Find a path P such that it passes through the
least number of border nodes.
* Objective functions are formulated using the following Description: Find a path P such that it passes through the least
terminology: number of border nodes.
+ A network comprises a set of N links {Li, (i=1...N)}. - OFs are formulated using the following terminology:
+ A path P is a list of K links {Lpi,(i=1...K)}. o A network comprises a set of N links {Li, (i=1...N)}.
+ D(Lpi) if a function that determines if the links Lpi o A path P is a list of K links {Lpi, (i=1...K)}.
and Lpi+1 belong to different domains, D(Li) = 1 if link
Li and Li+1 belong to different domains, D(Lk) = 0 if
link Lk and Lk+1 belong to the same domain.
+ The number of border node in a path P is denoted by B(P), o D(Lpi) is a function that determines if the links Lpi and
where B(P) = sum{D(Lpi),(i=1...K-1)}. Lpi+1 belong to different domains. D(Li) = 1 if link Li and
Li+1 belong to different domains; D(Lk) = 0 if link Lk and
Lk+1 belong to the same domain.
+ Find a path P such that B(P) is minimized. o The number of border nodes in a path P is denoted by B(P),
where B(P) = sum{D(Lpi), (i=1...K-1)}.
There is one objective function that applies to a set of o Find a path P such that B(P) is minimized.
synchronized path computation requests to increase the domain
diversity:
o MCTD There is one OF that applies to a set of synchronized PCReq messages
to increase the domain diversity:
* Name: Minimize the number of Common Transit Domains * MCTD
* Objective Function Code - TBD13 (to be assigned by IANA) Name: Minimize the number of Common Transit Domains (MCTD)
* Description: Find a set of paths such that it passes through OF code: 14
the least number of common transit domains.
+ A network comprises a set of N domains {Di, (i=1...N)}. Description: Find a set of paths such that it passes through the
least number of common transit domains.
+ A path P passes through K unique domains {Dpi,(i=1...K)}. - A network comprises a set of N domains {Di, (i=1...N)}.
+ A set of paths {P1...Pm} have L transit domains that are - A path P passes through K unique domains {Dpi, (i=1...K)}.
common to more than one path {Dpi,(i=1...L)}.
+ Find a set of paths such that the value of L is minimized. - A set of paths {P1...Pm} has L transit domains that are common
to more than one path {Dpi, (i=1...L)}.
- Find a set of paths such that the value of L is minimized.
3.4.2. OF Object 3.4.2. OF Object
The OF (Objective Function) object [RFC5541] is carried within a The OF object [RFC5541] is carried in a PCReq message so as to
PCReq message so as to indicate the desired/required objective indicate the desired/required OF to be applied by the PCE during path
function to be applied by the PCE during path computation. As per computation. As per Section 3.2 of [RFC5541], a single OF object may
Section 3.2 of [RFC5541] a single OF object may be included in a path be included in a PCReq message.
computation request.
The new OF codes described in Section 3.4.1 are applicable at the The new OF codes described in Section 3.4.1 are applicable to the
inter-domain path computation performed by the parent PCE, it is inter-domain path computation performed by the parent PCE. It is
also necessary to specify the OF code that may be applied for the also necessary to specify the OF code that may be applied for the
intra-domain path computation performed by the child PCE. To intra-domain path computation performed by the child PCE. To
accommodate this, the OF-List TLV (described in Section 2.1. of accommodate this, the OF-List TLV (described in Section 2.1 of
[RFC5541]) is included in the OF object as an optional TLV. [RFC5541]) is included in the OF object as an optional TLV.
The OF-List TLV allows encoding of multiple OF codes. When this TLV The OF-List TLV allows the encoding of multiple OF codes. When this
is included inside the OF object, only the first OF-code in the TLV is included inside the OF object, only the first OF code in the
OF-LIST TLV is considered. The parent PCE MUST use this OF code in OF-List TLV is considered. The parent PCE MUST use this OF code in
the OF object when sending the intra domain path computation request the OF object when sending the intra-domain PCReq message to the
to the child PCE. If the OF list TLV is included in the OF Object, child PCE. If the OF-List TLV is included in the OF object, the OF
the OF Code inside the OF Object MUST include one of the H-PCE code inside the OF object MUST include one of the H-PCE OFs defined
Objective Functions defined in this document, the OF Code inside the in this document. The OF code inside the OF-List TLV MUST NOT
OF List TLV MUST NOT include an H-PCE Objective Function. If this include an H-PCE OF. If this condition is not met, the PCEP speaker
condition is not met, the PCEP speaker MUST respond with a PCErr MUST respond with a PCErr message with Error-Type=10 (Reception of an
message with Error-Type=10 (Reception of an invalid object) and invalid object) and Error-Value=23 (Incompatible OF codes in H-PCE).
Error-Value=TBD15 (Incompatible OF codes in H-PCE).
If the Objective Functions defined in this document are unknown or If the OFs defined in this document are unknown or unsupported by a
unsupported by a PCE, then the procedure as defined in [RFC5541] PCE, then the procedure as defined in [RFC5440] is followed.
is followed.
3.5. Metric Object 3.5. METRIC Object
The METRIC object is defined in Section 7.8 of [RFC5440], comprising The METRIC object is defined in Section 7.8 of [RFC5440] and is
of metric-value, metric-type (T field) and flags. This document comprised of the metric-value field, the metric type (the T field),
defines the following types for the METRIC object for H-PCE: and flags (the Flags field). This document defines the following
types for the METRIC object for the H-PCE model:
o T=TBD6: Domain count metric (number of domains crossed); T=20: Domain Count metric (number of domains crossed).
o T=TBD7: Border Node count metric (number of border nodes crossed). T=21: Border Node Count metric (number of border nodes crossed).
The domain count metric type of the METRIC object encodes the number The Domain Count metric type of the METRIC object encodes the number
of domains crossed in the path. The border node count metric type of of domains crossed in the path. The Border Node Count metric type of
the METRIC object encodes the number of border nodes in the path. If the METRIC object encodes the number of border nodes in the path. If
a domain is re-entered, then domain should be double counted. a domain is re-entered, then the domain should be double counted.
A PCC or child PCE MAY use the metric in a PCReq message for an A PCC or child PCE MAY use the metric in a PCReq message for an
inter-domain path computation, meeting the number of domain or border inter-domain path computation, meeting the requirement for the number
nodes crossing requirement. As per [RFC5440], in this case, the B bit of domains or border nodes being crossed. As per [RFC5440], in this
is set to suggest a bound (a maximum) for the metric that must not be case, the B-bit is set to suggest a bound (a maximum) for the metric
exceeded for the PCC to consider the computed path as acceptable. that must not be exceeded for the PCC to consider the computed path
acceptable.
A PCC or child PCE MAY also use this metric to ask the PCE to A PCC or child PCE MAY also use this metric to ask the PCE to
optimize the metric during inter-domain path computation. In this optimize the metric during inter-domain path computation. In this
case, the B flag is cleared, and the C flag is set. case, the B-flag is cleared, and the C-flag is set.
The Parent PCE MAY use the metric in a PCRep message along with a The parent PCE MAY use the metric in a PCRep message along with a NO-
NO-PATH object in the case where the PCE cannot compute a path PATH object in the case where the PCE cannot compute a path that
meeting this constraint. A PCE MAY also use this metric to send the meets this constraint. A PCE MAY also use this metric to send the
computed end to end metric value in a reply message. computed end-to-end metric value in a reply message.
3.6. SVEC Object 3.6. SVEC Object
[RFC5440] defines SVEC object which includes flags for the potential [RFC5440] defines the Synchronization Vector (SVEC) object, which
dependency between the set of path computation requests (Link, Node includes flags for the potential dependency between the set of PCReq
and SRLG diverse). This document defines a new flag O for domain messages (Link, Node, and SRLG diverse). This document defines a new
diversity. flag (the O-bit) for domain diversity.
The following new bit is added to the Flags field: The following new bit is added to the Flags field:
o Domain Diverse O-bit - TBD14 : when set, this indicates that the Domain Diverse O-bit - 18:
computed paths corresponding to the requests specified by the When set, this indicates that the computed paths corresponding
following RP objects MUST NOT have any transit domains in to the requests specified by any RP objects that might be
common. provided MUST NOT have any transit domains in common.
The Domain Diverse O-bit can be used in Hierarchical PCE path The Domain Diverse O-bit can be used in H-PCE path computation to
computation to compute synchronized domain diverse end to end path or compute synchronized domain-diverse end-to-end paths or diverse
diverse domain sequences. domain sequences.
When domain diverse O bit is set, it is applied to the transit When the Domain Diverse O-bit is set, it is applied to the transit
domains. The other bit in SVEC object (N, L, S etc.) MAY be set and domains. The other bit in SVEC object L (Link diverse), N (Node
MUST still be applied in the ingress and egress shared domain. diverse), S (SRLG diverse), etc. MAY be set and MUST still be applied
in the ingress and egress shared domain.
3.7. PCEP-ERROR Object 3.7. PCEP-ERROR Object
3.7.1. Hierarchy PCE Error-Type 3.7.1. Hierarchical PCE Error-Type
A new PCEP Error-Type [RFC5440] is used for the H-PCE extension as A new PCEP Error-Type [RFC5440] is used for the H-PCE extension as
defined below: defined below:
+------------+-----------------------------------------+ +------------+------------------------------------------------------+
| Error-Type | Meaning | | Error-Type | Meaning |
+------------+-----------------------------------------+ +============+======================================================+
| TBD8 | H-PCE error | | 28 | H-PCE Error |
| | Error-value=1: H-PCE capability | | | |
| | was not advertised | | | Error-Value=1: H-PCE Capability not |
| | Error-value=2: parent PCE capability | | | advertised |
| | cannot be provided | | | |
+------------+-----------------------------------------+ | | Error-Value=2: Parent PCE Capability cannot |
| | be provided |
+------------+------------------------------------------------------+
Figure 4: H-PCE error Table 1: H-PCE Error
3.8. NO-PATH Object 3.8. NO-PATH Object
To communicate the reason(s) for not being able to find a multi- To communicate the reason(s) for not being able to find a multi-
domain path or domain sequence, the NO-PATH object can be used in the domain path or domain sequence, the NO-PATH object can be used in the
PCRep message. [RFC5440] defines the format of the NO-PATH object. PCRep message. [RFC5440] defines the format of the NO-PATH object.
The object may contain a NO-PATH-VECTOR TLV to provide additional The object may contain a NO-PATH-VECTOR TLV to provide additional
information about why a path computation has failed. information about why a path computation has failed.
Three new bit flags are defined to be carried in the Flags field in This document defines four new bit flags in the "NO-PATH-VECTOR TLV
the NO-PATH-VECTOR TLV carried in the NO-PATH Object. Flag Field" subregistry. These flags are to be carried in the Flags
field in the NO-PATH-VECTOR TLV carried in the NO-PATH object.
o Bit number TBD9: When set, the parent PCE indicates that Bit number 22: When set, the parent PCE indicates that the
destination domain unknown; destination domain is unknown.
o Bit number TBD10: When set, the parent PCE indicates unresponsive Bit number 21: When set, the parent PCE indicates that one or
child PCE(s); more child PCEs are unresponsive.
o Bit number TBD11: When set, the parent PCE indicates no available Bit number 20: When set, the parent PCE indicates that no
resource available in one or more domains. resources are available in one or more domains.
o Bit number TBD12: When set, the parent PCE indicates that Bit number 19: When set, the parent PCE indicates that the
the destination is not found in the indicated domain. destination is not found in the indicated domain.
4. H-PCE Procedures 4. H-PCE Procedures
The H-PCE path computation procedure is described in [RFC6805]. The H-PCE path computation procedure is described in [RFC6805].
4.1. OPEN Procedure between Child PCE and Parent PCE 4.1. OPEN Procedure between Child PCE and Parent PCE
If a child PCE wants to use the peer PCE as a parent, it MUST set the If a child PCE wants to use the peer PCE as a parent, it MUST set the
P (parent PCE request flag) in the H-PCE-CAPABILITY TLV inside the P-flag (Parent PCE Request flag) in the H-PCE-CAPABILITY TLV inside
OPEN object carried in the Open message during the PCEP session the OPEN object carried in the Open message during the PCEP session
initialization procedure. initialization procedure.
The child PCE MAY also report its list of domain IDs, to the parent The child PCE MAY also report its list of domain IDs to the parent
PCE, by specifying them in the Domain-ID TLVs in the OPEN object. PCE by specifying them in the Domain-ID TLVs in the OPEN object.
This object is carried in the OPEN message during the PCEP session This object is carried in the Open message during the PCEP session
initialization procedure initialization procedure.
The OF codes defined in this document can be carried in the OF-list The OF codes defined in this document can be carried in the OF-List
TLV of the OPEN object. If the OF-list TLV carries the OF codes, it TLV of the OPEN object. If the OF-List TLV carries the OF codes, it
means that the PCE is capable of implementing the corresponding means that the PCE is capable of implementing the corresponding OFs.
objective functions. This information can be used for selecting a This information can be used for selecting a proper parent PCE when a
proper parent PCE when a child PCE wants to get a path that satisfies child PCE wants to get a path that satisfies a certain OF.
a certain Objective Function.
When a child PCE sends a PCReq to a peer PCE, which requires parental When a child PCE sends a PCReq to a peer PCE that requires parental
activity and H-PCE capability flags TLV but which were not included activity and the H-PCE-CAPABILITY TLV but these items were not taken
in the session establishment procedure described above, the peer PCE into account in the session establishment procedure described above,
SHOULD send a PCErr message to the child PCE and MUST specify the the peer PCE SHOULD send a PCErr message to the child PCE and MUST
error-type=TBD8 (H-PCE error) and error-value=1 (H-PCE capability was specify Error-Type=28 (H-PCE Error) and Error-Value=1 (H-PCE
not advertised) in the PCEP-ERROR object. Capability not advertised) in the PCEP-ERROR object.
When a specific child PCE sends a PCReq to a peer PCE, that requires When a specific child PCE sends a PCReq to a peer PCE that requires
parental activity and the peer PCE does not want to act as the parent parental activity and the peer PCE does not want to act as the parent
for it, the peer PCE SHOULD send a PCErr message to the child PCE and for it, the peer PCE SHOULD send a PCErr message to the child PCE and
MUST specify the error-type=TBD8 (H-PCE error) and error-value=2 MUST specify Error-Type=28 (H-PCE Error) and Error-Value=2 (Parent
(Parent PCE capability cannot be provided) in the PCEP-ERROR object. PCE Capability cannot be provided) in the PCEP-ERROR object.
4.2. Procedure to Obtain Domain Sequence 4.2. Procedure for Obtaining the Domain Sequence
If a child PCE only wants to get the domain sequence for a multi- If a child PCE only wants to get the domain sequence for a multi-
domain path computation from a parent PCE, it can set the Domain Path domain path computation from a parent PCE, it can set the Domain Path
Request bit in the H-PCE-FLAG TLV in the RP object carried in a PCReq Request bit in the H-PCE-FLAG TLV in the RP object carried in a PCReq
message. The parent PCE which receives the PCReq message tries to message. The parent PCE that receives the PCReq message tries to
compute a domain sequence for it (instead of the E2E path). If the compute a domain sequence for it (instead of the end-to-end path).
domain path computation succeeds the parent PCE sends a PCRep message If the domain path computation succeeds, the parent PCE sends a PCRep
which carries the domain sequence in the Explicit Route Object (ERO) message that carries the domain sequence in the Explicit Route Object
to the child PCE. Refer to [RFC7897] for more details about domain (ERO) to the child PCE. Refer to [RFC7897] for more details about
sub-objects in the ERO. Otherwise, it sends a PCReq message which domain subobjects in the ERO. Otherwise, it sends a PCReq message
carries the NO-PATH object to the child PCE. that carries the NO-PATH object to the child PCE.
5. Error Handling 5. Error Handling
A PCE that is capable of acting as a parent PCE might not be A PCE that is capable of acting as a parent PCE might not be
configured or willing to act as the parent for a specific child PCE. configured or willing to act as the parent for a specific child PCE.
This fact could be determined when the child sends a PCReq that When the child PCE sends a PCReq that requires parental activity, a
requires parental activity, and could result in a negative response negative response in the form of a PCEP Error (PCErr) message that
in a PCEP Error (PCErr) message and indicate the hierarchy PCE error- includes H-PCE Error-Type=28 (H-PCE Error) and an applicable Error-
type=TBD8 (H-PCE error) and suitable error-value. (Section 3.7) Value (Section 3.7) might result.
Additionally, the parent PCE may fail to find the multi-domain path Additionally, the parent PCE may fail to find the multi-domain path
or domain sequence due to one or more of the following reasons: or domain sequence for one or more of the following reasons:
o A child PCE cannot find a suitable path to the egress; * A child PCE cannot find a suitable path to the egress.
o The parent PCE does not hear from a child PCE for a specified * The parent PCE does not hear from a child PCE for a specified
time; time.
o The Objective Functions specified in the path request cannot be * The OFs specified in the path request cannot be met.
met.
In this case, the parent PCE MAY need to send a negative path In this case, the parent PCE MAY need to send a negative PCRep
computation reply specifying the reason. This can be achieved by message specifying the reason for the failure. This can be achieved
including NO-PATH object in the PCRep message. Extension to NO-PATH by including the NO-PATH object in the PCRep message. An extension
object is needed to include the aforementioned reasons described in to the NO-PATH object is needed in order to include the reasons
Section 3.7. defined in Section 3.8.
6. Manageability Considerations 6. Manageability Considerations
General PCE and PCEP management considerations are discussed in General PCE and PCEP management/manageability considerations are
[RFC4655] and [RFC5440]. There are additional management discussed in [RFC4655] and [RFC5440]. There are additional
considerations for H-PCE which are described in [RFC6805], and management considerations for the H-PCE model; these are described in
repeated in this section. [RFC6805] and repeated in this section.
The administrative entity responsible for the management of the The administrative entity responsible for the management of the
parent PCEs must be determined for the following cases: parent PCEs must be determined for the following cases:
o multi-domains (e.g., IGP areas or multiple ASes) within a single * Multiple domains (e.g., IGP areas or multiple ASes) in a single
service provider network, the management responsibility for the service provider network. The management responsibility for the
parent PCE would most likely be handled by the service provider, parent PCE would most likely be handled by the service provider.
o multiple ASes within different service provider networks, it may * Multiple ASes in different service provider networks. It may be
be necessary for a third party to manage the parent PCEs according necessary for a third party to manage the parent PCEs according to
to commercial and policy agreements from each of the participating commercial and policy agreements from each of the participating
service providers. service providers.
6.1. Control of Function and Policy 6.1. Control of Function and Policy
Control and function will need to be carefully managed in an H-PCE Control of H-PCE function will need to be carefully managed via
network. A child PCE will need to be configured with the address of configuration and interaction policies, which may be controlled via a
its parent PCE. It is expected that there will only be one or two policy module on the H-PCE. A child PCE will need to be configured
parents of any child. with the address of its parent PCE. It is expected that there will
only be one or two parents of any child.
The parent PCE also needs to be aware of the child PCEs for all child The parent PCE also needs to be aware of the child PCEs for all child
domains that it can see. This information is most likely to be domains that it can see. This information is most likely to be
configured (as part of the administrative definition of each domain). configured (as part of the administrative definition of each domain).
Discovery of the relationships between parent PCEs and child PCEs Discovery of the relationships between parent PCEs and child PCEs
do not form part of the hierarchical PCE architecture. Mechanisms does not form part of the H-PCE architecture. Mechanisms that rely
that rely on advertising or querying PCE locations across domain or on advertising or querying PCE locations across domain or provider
provider boundaries are undesirable for security, scaling, boundaries are undesirable for security, scaling, commercial, and
commercial, and confidentiality reasons. The specific behaviour of confidentiality reasons. The specific behavior of the child and
the child and parent PCE are described in the following sub-sections. parent PCEs is described in the following subsections.
6.1.1. Child PCE 6.1.1. Child PCE
Support of the hierarchical procedure will be controlled by the Support of the hierarchical procedure will be controlled by the
management organization responsible for each child PCE. A child PCE management organization responsible for each child PCE. A child PCE
must be configured with the address of its parent PCE in order for it must be configured with the address of its parent PCE in order for it
to interact with its parent PCE. The child PCE must also be to interact with its parent PCE. The child PCE must also be
authorized to peer with the parent PCE. authorized to peer with the parent PCE.
6.1.2. Parent PCE 6.1.2. Parent PCE
The parent PCE MUST only accept path computation requests from The parent PCE MUST only accept PCReq messages from authorized child
authorized child PCEs. If a parent PCE receives requests from an PCEs. If a parent PCE receives requests from an unauthorized child
unauthorized child PCE, the request SHOULD be dropped. This means PCE, the request SHOULD be dropped. This means that a parent PCE
that a parent PCE MUST be able to cryptographically authenticate MUST be able to cryptographically authenticate requests from child
requests from child PCEs. PCEs.
Multi-party shared key authentication schemes are not recommended for Multi-party shared key authentication schemes are not recommended for
inter-domain relationships because of the potential for impersonation inter-domain relationships because of (1) the potential for
and repudiation and for the operational difficulties should impersonation and repudiation and (2) operational difficulties should
revocation be required. revocation be required.
The choice of authentication schemes to employ may be left to The choice of authentication schemes to employ may be left to
implementers of H-PCE and are not discussed further in this document. implementers of the H-PCE architecture and are not discussed further
in this document.
6.1.3. Policy Control 6.1.3. Policy Control
It may be necessary to maintain a policy module on the parent PCE It may be necessary to maintain H-PCE policy [RFC5394] via a policy
[RFC5394]. This would allow the parent PCE to apply commercially control module on the parent PCE. This would allow the parent PCE to
relevant constraints such as SLAs, security, peering preferences, and apply commercially relevant constraints such as SLAs, security,
monetary costs. peering preferences, and monetary costs.
It may also be necessary for the parent PCE to limit the It may also be necessary for the parent PCE to limit the end-to-end
end-to-end path selection by including or excluding specific domains path selection by including or excluding specific domains based on
based on commercial relationships, security implications, and commercial relationships, security implications, and reliability.
reliability.
6.2. Information and Data Models 6.2. Information and Data Models
A MIB module for PCEP was published as RFC 7420 [RFC7420] that [RFC7420] provides a MIB module for PCEP and describes managed
describes managed objects for modelling of PCEP communication. A objects for the modeling of PCEP communication. A YANG module for
YANG module for PCEP has also been proposed [I-D.ietf-pce-pcep-yang]. PCEP has also been proposed [PCEP-YANG].
Additionally, H-PCE MIB module, or additional data model, will be An H-PCE MIB module or an additional data model will also be required
required to report parent PCE and child PCE information, including: for reporting parent PCE and child PCE information, including:
o parent PCE configuration and status, * parent PCE configuration and status,
o child PCE configuration and information, * child PCE configuration and information,
o notifications to indicate session changes between parent PCEs and * notifications to indicate session changes between parent PCEs and
child PCEs, and child PCEs, and
o notification of parent PCE TED updates and changes. * notification of parent PCE TED updates and changes.
6.3. Liveness Detection and Monitoring 6.3. Liveness Detection and Monitoring
The hierarchical procedure requires interaction with multiple PCEs. The hierarchical procedure requires interaction with multiple PCEs.
Once a child PCE requests an end-to-end path, a sequence of events Once a child PCE requests an end-to-end path, a sequence of events
occurs that requires interaction between the parent PCE and each occurs that requires interaction between the parent PCE and each
child PCE. If a child PCE is not operational, and an alternate child PCE. If a child PCE is not operational and an alternate
transit domain is not available, then the failure must be reported. transit domain is not available, then the failure must be reported.
6.4. Verify Correct Operations 6.4. Verifying Correct Operations
Verifying the correct operation of a parent PCE can be performed by Verifying the correct operation of a parent PCE can be performed by
monitoring a set of parameters. The parent PCE implementation should monitoring a set of parameters. The parent PCE implementation should
provide the following parameters monitored at the parent PCE: provide the following parameters monitored at the parent PCE:
o number of child PCE requests, * number of child PCE requests,
o number of successful hierarchical PCE procedures completions on a * number of successful H-PCE procedure completions on a per-PCE-peer
per-PCE-peer basis, basis,
o number of hierarchical PCE procedure completion failures on a per- * number of H-PCE procedure-completion failures on a per-PCE-peer
PCE-peer basis, and basis, and
o number of hierarchical PCE procedure requests from unauthorized * number of H-PCE procedure requests from unauthorized child PCEs.
child PCEs.
6.5. Requirements On Other Protocols 6.5. Requirements on Other Protocols
Mechanisms defined in this document do not imply any new requirements Mechanisms defined in this document do not imply any new requirements
on other protocols. on other protocols.
6.6. Impact On Network Operations 6.6. Impact on Network Operations
The hierarchical PCE procedure is a multiple-PCE path computation The H-PCE procedure is a multiple-PCE path computation scheme.
scheme. Subsequent requests to and from the child and parent PCEs do Subsequent requests to and from the child and parent PCEs do not
not differ from other path computation requests and should not have differ from other path computation requests and should not have any
any significant impact on network operations. significant impact on network operations.
7. IANA Considerations 7. IANA Considerations
IANA maintains the "Path Computation Element Protocol (PCEP) Numbers" IANA maintains the "Path Computation Element Protocol (PCEP) Numbers"
registry. This document requests IANA actions to allocate code registry. IANA has allocated code points for the protocol elements
points for the protocol elements defined in this document. defined in this document.
7.1. PCEP TLV Type Indicators 7.1. PCEP TLV Type Indicators
IANA Manages the PCEP TLV code point registry (see [RFC5440]). This IANA maintains the "PCEP TLV Type Indicators" subregistry (see
is maintained as the "PCEP TLV Type Indicators" sub-registry of the [RFC5440]) within the "Path Computation Element Protocol (PCEP)
"Path Computation Element Protocol (PCEP) Numbers" registry. Numbers" registry.
This document defines three new PCEP TLVs. IANA is requested to make IANA has allocated the following three new PCEP TLVs:
the following allocation:
Type TLV name References +------+------------------+-----------+
----------------------------------------------- | Type | TLV Name | Reference |
TBD1 H-PCE-CAPABILITY TLV This I-D +======+==================+===========+
TBD2 Domain-ID TLV This I-D | 13 | H-PCE-CAPABILITY | RFC 8685 |
TBD3 H-PCE-FLAG TLV This I-D +------+------------------+-----------+
| 14 | Domain-ID | RFC 8685 |
+------+------------------+-----------+
| 15 | H-PCE-FLAG | RFC 8685 |
+------+------------------+-----------+
Table 2: New PCEP TLVs
7.2. H-PCE-CAPABILITY TLV Flags 7.2. H-PCE-CAPABILITY TLV Flags
This document requests that a new sub-registry, named "H-PCE- IANA has created the "H-PCE-CAPABILITY TLV Flag Field" subregistry
CAPABILITY TLV Flag Field", is created within the "Path Computation within the "Path Computation Element Protocol (PCEP) Numbers"
Element Protocol (PCEP) Numbers" registry to manage the Flag field in registry to manage the Flag field in the H-PCE-CAPABILITY TLV of the
the H-PCE-CAPABILITY TLV of the PCEP OPEN object. PCEP OPEN object.
New values are to be assigned by Standards Action [RFC8126]. Each New values are assigned by Standards Action [RFC8126]. Each
bit should be tracked with the following qualities: registered bit should include the following information:
o Bit number (counting from bit 0 as the most significant bit) * Bit number (counting from bit 0 as the most significant bit)
o Capability description * Capability description
o Defining RFC * Defining RFC
The following values are defined in this document: The following value is defined in this document:
Bit Description Reference +-----+----------------------------+-----------+
-------------------------------------------------- | Bit | Description | Reference |
31 P (Parent PCE Request bit) This I.D. +=====+============================+===========+
| 31 | P (Parent PCE Request bit) | RFC 8685 |
+-----+----------------------------+-----------+
7.3. Domain-ID TLV Domain type Table 3: Parent PCE Request Bit
This document requests that a new sub-registry, named "Domain-ID TLV 7.3. Domain-ID TLV Domain Type
Domain type", is created within the "Path Computation Element
Protocol (PCEP) Numbers" registry to manage the Domain-Type field of
the Domain-ID TLV. The allocation policy for this new sub-registry is
IETF Review [RFC8126].
Value Meaning IANA has created the "Domain-ID TLV Domain Type" subregistry within
----------------------------------------------- the "Path Computation Element Protocol (PCEP) Numbers" registry to
1 2-byte AS number manage the Domain Type field of the Domain-ID TLV. The allocation
2 4-byte AS number policy for this new subregistry is IETF Review [RFC8126].
3 4-byte OSPF area ID
4 Variable length IS-IS area ID The following values are defined in this document:
+-------+-------------------------------+
| Value | Meaning |
+=======+===============================+
| 0 | Reserved |
+-------+-------------------------------+
| 1 | 2-byte AS number |
+-------+-------------------------------+
| 2 | 4-byte AS number |
+-------+-------------------------------+
| 3 | 4-byte OSPF area ID |
+-------+-------------------------------+
| 4 | Variable-length IS-IS area ID |
+-------+-------------------------------+
| 5-255 | Unassigned |
+-------+-------------------------------+
Table 4: Parameters for Domain-ID TLV
Domain Type
7.4. H-PCE-FLAG TLV Flags 7.4. H-PCE-FLAG TLV Flags
This document requests that a new sub-registry, named "H-PCE-FLAG IANA has created the "H-PCE-FLAG TLV Flag Field" subregistry within
TLV Flag Field", is created within the "Path Computation Element the "Path Computation Element Protocol (PCEP) Numbers" registry to
Protocol (PCEP) Numbers" registry to manage the Flag field in the H- manage the Flag field in the H-PCE-FLAG TLV of the PCEP RP object.
PCE-FLAGS TLV of the PCEP RP object. New values are to be assigned New values are to be assigned by Standards Action [RFC8126]. Each
by Standards Action [RFC8126]. Each bit should be tracked with the registered bit should include the following information:
following qualities:
o Bit number (counting from bit 0 as the most significant bit) * Bit number (counting from bit 0 as the most significant bit)
o Capability description * Capability description
o Defining RFC * Defining RFC
The following values are defined in this document: The following values are defined in this document:
Bit Description Reference +-----+----------------------------------+-----------+
----------------------------------------------- | Bit | Description | Reference |
31 S (Domain This I.D. +=====+==================================+===========+
Sequence bit) | 30 | D (Disallow Domain Re-entry bit) | RFC 8685 |
30 D (Disallow Domain This I.D. +-----+----------------------------------+-----------+
Re-entry bit) | 31 | S (Domain Sequence bit) | RFC 8685 |
+-----+----------------------------------+-----------+
Table 5: New H-PCE-FLAG TLV Flag Field Entries
7.5. OF Codes 7.5. OF Codes
IANA maintains a registry of Objective Function (described in IANA maintains a list of OFs (described in [RFC5541]) in the
[RFC5541]) at the sub-registry "Objective Function". Three new "Objective Function" subregistry within the "Path Computation Element
Objective Functions have been defined in this document. Protocol (PCEP) Numbers" registry.
IANA is requested to make the following allocations: IANA has allocated the following OFs:
Code +------------+-------------------------------+-----------+
Point Name Reference | Code Point | Name | Reference |
------------------------------------------------------ +============+===============================+===========+
TBD4 Minimum number of Transit This I.D. | 12 | Minimize the number of | RFC 8685 |
Domains (MTD) | | Transit Domains (MTD) | |
TBD5 Minimize number of Border This I.D. +------------+-------------------------------+-----------+
Nodes (MBN) | 13 | Minimize the number of Border | RFC 8685 |
TBD13 Minimize the number of This I.D. | | Nodes (MBN) | |
Common Transit Domains +------------+-------------------------------+-----------+
(MCTD) | 14 | Minimize the number of Common | RFC 8685 |
| | Transit Domains (MCTD) | |
+------------+-------------------------------+-----------+
7.6. METRIC Types Table 6: New OF Codes
IANA maintains one sub-registry for "METRIC object T field". Two new 7.6. METRIC Object Types
metric types are defined in this document for the METRIC object
(specified in [RFC5440]).
IANA is requested to make the following allocations: IANA maintains the "METRIC Object T Field" subregistry [RFC5440]
within the "Path Computation Element Protocol (PCEP) Numbers"
registry.
Value Description Reference The following two new metric types for the METRIC object are defined
---------------------------------------------------------- in this document:
TBD6 Domain Count metric This I.D.
TBD7 Border Node Count metric This I.D. +-------+--------------------------+-----------+
| Value | Description | Reference |
+=======+==========================+===========+
| 20 | Domain Count metric | RFC 8685 |
+-------+--------------------------+-----------+
| 21 | Border Node Count metric | RFC 8685 |
+-------+--------------------------+-----------+
Table 7: New METRIC Object Types
7.7. New PCEP Error-Types and Values 7.7. New PCEP Error-Types and Values
IANA maintains a registry of Error-Types and Error-values for use in IANA maintains a list of Error-Types and Error-Values for use in PCEP
PCEP messages. This is maintained as the "PCEP-ERROR Object Error messages. This list is maintained in the "PCEP-ERROR Object Error
Types and Values" sub-registry of the "Path Computation Element Types and Values" subregistry within the "Path Computation Element
Protocol (PCEP) Numbers" registry. Protocol (PCEP) Numbers" registry.
IANA is requested to make the following allocations: IANA has allocated the following:
Error-Type Meaning and error values Reference
------------------------------------------------------
TBD8 H-PCE Error This I.D.
Error-value=1 H-PCE +------------+------------------------------------------+-----------+
Capability not advertised | Error-Type | Meaning and Error Values | Reference |
+============+==========================================+===========+
| 28 | H-PCE Error | RFC 8685 |
| | | |
| | Error-Value=1: H-PCE Capability | |
| | not advertised | |
| | | |
| | Error-Value=2: Parent PCE | |
| | Capability cannot be provided | |
+------------+------------------------------------------+-----------+
| 10 | Reception of an invalid object | RFC 5440 |
| | | |
| | Error-Value=23: Incompatible OF | RFC 8685 |
| | codes in H-PCE | |
+------------+------------------------------------------+-----------+
Error-value=2 Parent PCE Table 8: New PCEP Error-Types and Values
Capability cannot be provided
10 Reception of an invalid object [RFC5440] 7.8. New NO-PATH-VECTOR TLV Bit Flag
Error-value=TBD15: Incompatible This I.D. IANA maintains the "NO-PATH-VECTOR TLV Flag Field" subregistry, which
OF codes in H-PCE contains a list of bit flags carried in the PCEP NO-PATH-VECTOR TLV
in the PCEP NO-PATH object as defined in [RFC5440].
7.8. New NO-PATH-VECTOR TLV Bit Flag IANA has allocated the following four new bit flags:
IANA maintains a sub-registry "NO-PATH-VECTOR TLV Flag Field" of +------------+----------------------------+-----------+
bit flags carried in the PCEP NO-PATH-VECTOR TLV in the PCEP NO-PATH | Bit Number | Description | Reference |
object as defined in [RFC5440]. IANA is requested to assign three +============+============================+===========+
new bit flag as follows: | 22 | Destination domain unknown | RFC 8685 |
+------------+----------------------------+-----------+
| 21 | Unresponsive child PCE(s) | RFC 8685 |
+------------+----------------------------+-----------+
| 20 | No available resource in | RFC 8685 |
| | one or more domains | |
+------------+----------------------------+-----------+
| 19 | Destination is not found | RFC 8685 |
| | in the indicated domain | |
+------------+----------------------------+-----------+
Bit Number Name Flag Reference Table 9: PCEP NO-PATH Object Flags
------------------------------------------------------
TBD9 Destination Domain unknown This I.D.
TBD10 Unresponsive child PCE(s) This I.D.
TBD11 No available resource in This I.D.
one or more domain
TBD12 Destination is not found This I.D.
in the indicated domain.
7.9. SVEC Flag 7.9. SVEC Flag
IANA maintains a sub-registry "SVEC Object Flag Field" of bit flags IANA maintains the "SVEC Object Flag Field" subregistry, which
carried in the PCEP SVEC object as defined in [RFC5440]. IANA is contains a list of bit flags carried in the PCEP SVEC object as
requested to assign one new bit flag as follows: defined in [RFC5440].
Bit Number Name Flag Reference IANA has allocated the following new bit flag:
------------------------------------------------------
TBD14 Domain Diverse O-bit This I.D. +------------+----------------------+-----------+
| Bit Number | Description | Reference |
+============+======================+===========+
| 18 | Domain Diverse O-bit | RFC 8685 |
+------------+----------------------+-----------+
Table 10: Domain Diverse O-Bit
8. Security Considerations 8. Security Considerations
The hierarchical PCE procedure relies on PCEP and inherits the The H-PCE procedure relies on PCEP and inherits the security
security considerations defined in [RFC5440]. As PCEP operates over considerations defined in [RFC5440]. As PCEP operates over TCP, it
TCP, it may also make use of TCP security mechanisms, such as TCP may also make use of TCP security mechanisms, such as the TCP
Authentication Option (TCP-AO) [RFC5925] or Transport Layer Authentication Option (TCP-AO) [RFC5925] or Transport Layer Security
Security (TLS) [RFC8253]. (TLS) [RFC8253] [RFC8446].
Any multi-domain operation necessarily involves the exchange of Any multi-domain operation necessarily involves the exchange of
information across domain boundaries. This may represent a information across domain boundaries. This may represent a
significant security and confidentiality risk especially when the significant security and confidentiality risk, especially when the
child domains are controlled by different commercial concerns. PCEP child domains are controlled by different commercial concerns. PCEP
allows individual PCEs to maintain the confidentiality of their allows individual PCEs to maintain the confidentiality of their
domain path information using path-keys [RFC5520], and the H-PCE domain path information using path-keys [RFC5520], and the H-PCE
architecture is specifically designed to enable as much isolation of architecture is specifically designed to enable as much isolation of
domain topology and capabilities information as is possible. information related to domain topology and capabilities as possible.
For further considerations of the security issues related to inter-AS
path computation, see [RFC5376].
9. Contributing Authors
Xian Zhang
Huawei
EMail: zhang.xian@huawei.com
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: dhruv.ietf@gmail.com
10.Acknowledgements
The authors would like to thank Mike McBride, Kyle Rose, Roni Even For further considerations regarding the security issues related to
for their detailed review, comments and suggestions which helped inter-AS path computation, see [RFC5376].
improve this document.
11. References 9. References
11.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440, Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009, DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>. <https://www.rfc-editor.org/info/rfc5440>.
skipping to change at page 25, line 35 skipping to change at line 1204
[RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
Objective Functions in the Path Computation Element Objective Functions in the Path Computation Element
Communication Protocol (PCEP)", RFC 5541, Communication Protocol (PCEP)", RFC 5541,
DOI 10.17487/RFC5541, June 2009, DOI 10.17487/RFC5541, June 2009,
<https://www.rfc-editor.org/info/rfc5541>. <https://www.rfc-editor.org/info/rfc5541>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References 9.2. Informative References
[RFC4105] Le Roux, J., Ed., Vasseur, J., Ed., and J. Boyle, Ed., [RFC4105] Le Roux, J.-L., Ed., Vasseur, J.-P., Ed., and J. Boyle,
"Requirements for Inter-Area MPLS Traffic Engineering", Ed., "Requirements for Inter-Area MPLS Traffic
RFC 4105, DOI 10.17487/RFC4105, June 2005, Engineering", RFC 4105, DOI 10.17487/RFC4105, June 2005,
<https://www.rfc-editor.org/info/rfc4105>. <https://www.rfc-editor.org/info/rfc4105>.
[RFC4216] Zhang, R., Ed. and J. Vasseur, Ed., "MPLS Inter-Autonomous [RFC4216] Zhang, R., Ed. and J.-P. Vasseur, Ed., "MPLS Inter-
System (AS) Traffic Engineering (TE) Requirements", Autonomous System (AS) Traffic Engineering (TE)
RFC 4216, DOI 10.17487/RFC4216, November 2005, Requirements", RFC 4216, DOI 10.17487/RFC4216, November
<https://www.rfc-editor.org/info/rfc4216>. 2005, <https://www.rfc-editor.org/info/rfc4216>.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Element (PCE)-Based Architecture", RFC 4655, Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006, DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>. <https://www.rfc-editor.org/info/rfc4655>.
[RFC4726] Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for [RFC4726] Farrel, A., Vasseur, J.-P., and A. Ayyangar, "A Framework
Inter-Domain Multiprotocol Label Switching Traffic for Inter-Domain Multiprotocol Label Switching Traffic
Engineering", RFC 4726, DOI 10.17487/RFC4726, November Engineering", RFC 4726, DOI 10.17487/RFC4726, November
2006, <https://www.rfc-editor.org/info/rfc4726>. 2006, <https://www.rfc-editor.org/info/rfc4726>.
[RFC5152] Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang, "A [RFC5152] Vasseur, JP., Ed., Ayyangar, A., Ed., and R. Zhang, "A
Per-Domain Path Computation Method for Establishing Inter- Per-Domain Path Computation Method for Establishing Inter-
Domain Traffic Engineering (TE) Label Switched Paths Domain Traffic Engineering (TE) Label Switched Paths
(LSPs)", RFC 5152, DOI 10.17487/RFC5152, February 2008, (LSPs)", RFC 5152, DOI 10.17487/RFC5152, February 2008,
<https://www.rfc-editor.org/info/rfc5152>. <https://www.rfc-editor.org/info/rfc5152>.
[RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS [RFC5376] Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS
skipping to change at page 27, line 4 skipping to change at line 1269
[RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the [RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the
Path Computation Element Architecture to the Determination Path Computation Element Architecture to the Determination
of a Sequence of Domains in MPLS and GMPLS", RFC 6805, of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
DOI 10.17487/RFC6805, November 2012, DOI 10.17487/RFC6805, November 2012,
<https://www.rfc-editor.org/info/rfc6805>. <https://www.rfc-editor.org/info/rfc6805>.
[RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path [RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path
Computation Element Architecture", RFC 7399, Computation Element Architecture", RFC 7399,
DOI 10.17487/RFC7399, October 2014, DOI 10.17487/RFC7399, October 2014,
<http://www.rfc-editor.org/info/rfc7399>. <https://www.rfc-editor.org/info/rfc7399>.
[RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J. [RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
Hardwick, "Path Computation Element Communication Protocol Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module", (PCEP) Management Information Base (MIB) Module",
RFC 7420, DOI 10.17487/RFC7420, December 2014, RFC 7420, DOI 10.17487/RFC7420, December 2014,
<https://www.rfc-editor.org/info/rfc7420>. <https://www.rfc-editor.org/info/rfc7420>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752, Traffic Engineering (TE) Information Using BGP", RFC 7752,
skipping to change at page 27, line 34 skipping to change at line 1299
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the "PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)", Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017, RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>. <https://www.rfc-editor.org/info/rfc8253>.
[I-D.ietf-pce-pcep-yang] [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
YANG Data Model for Path Computation Element <https://www.rfc-editor.org/info/rfc8446>.
Communications Protocol (PCEP)", draft-ietf-pce-pcep-
yang-11 (work in progress), March 2019.
[I-D.ietf-pce-stateful-hpce] [PCEP-YANG]
Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., King, D., Dhody, D., Ed., Hardwick, J., Beeram, V., and J. Tantsura,
and O. Dios, "Hierarchical Stateful Path Computation "A YANG Data Model for Path Computation Element
Element (PCE).", draft-ietf-pce-stateful-hpce-07 (work in Communications Protocol (PCEP)", Work in Progress,
progress), April 2019. Internet-Draft, draft-ietf-pce-pcep-yang-13, 31 October
2019,
<https://tools.ietf.org/html/draft-ietf-pce-pcep-yang-13>.
[I-D.dhodylee-pce-pcep-ls] [STATEFUL-HPCE]
Dhody, D., Lee, Y., and D. Ceccarelli, "PCEP Extension for Dhody, D., Lee, Y., Ceccarelli, D., Shin, J., and D. King,
Distribution of Link-State and TE Information.", draft- "Hierarchical Stateful Path Computation Element (PCE)",
dhodylee-pce-pcep-ls-13 (work in progress), February 2019. Work in Progress, Internet-Draft, draft-ietf-pce-stateful-
hpce-15, 20 October 2019, <https://tools.ietf.org/html/
draft-ietf-pce-stateful-hpce-15>.
[PCEP-LS] Dhody, D., Lee, Y., and D. Ceccarelli, "PCEP Extension for
Distribution of Link-State and TE Information.", Work in
Progress, Internet-Draft, draft-dhodylee-pce-pcep-ls-14,
21 October 2019, <https://tools.ietf.org/html/draft-
dhodylee-pce-pcep-ls-14>.
Acknowledgements
The authors would like to thank Mike McBride, Kyle Rose, and Roni
Even for their detailed review, comments, and suggestions, which
helped improve this document.
Contributors
The following people contributed substantially to the content of this
document and should be considered coauthors:
Xian Zhang
Huawei
Email: zhang.xian@huawei.com
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore 560066
Karnataka
India
Email: dhruv.ietf@gmail.com
Authors' Addresses Authors' Addresses
Fatai Zhang Fatai Zhang
Huawei Huawei
Huawei Base, Bantian, Longgang District Huawei Base, Bantian, Longgang District
Shenzhen 518129 Shenzhen, 518129
China China
EMail: zhangfatai@huawei.com Email: zhangfatai@huawei.com
Quintin Zhao Quintin Zhao
Huawei Huawei
125 Nagog Technology Park 125 Nagog Technology Park
Acton, MA 01719 Acton, MA 01719
USA United States of America
EMail: quintin.zhao@huawei.com Email: quintinzhao@gmail.com
Oscar Gonzalez de Dios Oscar Gonzalez de Dios
Telefonica Telefonica I+D
Don Ramon de la Cruz 82-84 Don Ramon de la Cruz 82-84
Madrid 28045 28045 Madrid
Spain Spain
EMail: oscar.gonzalezdedios@telefonica.com Email: oscar.gonzalezdedios@telefonica.com
Ramon Casellas Ramon Casellas
CTTC CTTC
Av. Carl Friedrich Gauss n.7 Av. Carl Friedrich Gauss n.7
Barcelona, Castelldefels Castelldefels Barcelona
Spain Spain
EMail: ramon.casellas@cttc.es Email: ramon.casellas@cttc.es
Daniel King Daniel King
Old Dog Consulting Old Dog Consulting
UK United Kingdom
EMail: daniel@olddog.co.uk
Appendix
A1. Implementation Status
The H-PCE architecture and protocol procedures describe in this I-D
were implemented and tested for a variety of optical research
applications.
The Appendix should be removed before publication.
A1.1. Inter-layer traffic engineering with H-PCE
This work was led by:
o Ramon Casellas [ramon.casellas@cttc.es]
o Centre Tecnologic de Telecomunicacions de Catalunya (CTTC)
The H-PCE instances (parent and child) were multi-threaded
asynchronous processes. Implemented in C++11, using C++ Boost
Libraries. The targeted system used to deploy and run H-PCE
applications was a POSIX system (Debian GNU/Linux operating system).
Some parts of the software may require a Linux Kernel, the
availability of a Routing Controller running collocated in the same
host and the usage of libnetfilter / libipq and GNU/Linux firewalling
capabilities. Most of the functionality, including algorithms is
done by means of plugins (e.g., as shared libraries or .so files in
Unix systems).
The CTTC PCE supports the H-PCE architecture, but also supports
stateful PCE with active capabilities, as an OpenFlow controller, and
has dedicated plugins to support monitoring, BRPC, P2MP, path keys,
back end PCEs. Management of the H-PCE entities was supported via
HTTP and CLI via Telnet.
Further details of the H-PCE prototyping and experimentation can be
found in the following scientific papers:
R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I.
Morita, "Inter-layer traffic engineering with hierarchical-PCE in
MPLS-TP over wavelength switched optical networks" , Optics
Express, Vol. 20, No. 28, December 2012.
R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I.
Morita, M. Msurusawa, "Dynamic virtual link mesh topology
aggregation in multi-domain translucent WSON with hierarchical-
PCE", Optics Express Journal, Vol. 19, No. 26, December 2011.
R. Casellas, R. Munoz, R. Martinez, R. Vilalta, L. Liu, T.
Tsuritani, I. Morita, V. Lopez, O. Gonzalez de Dios, J. P.
Fernandez-Palacios, "SDN based Provisioning Orchestration of
OpenFlow/GMPLS Flexi-grid Networks with a Stateful Hierarchical
PCE", in Proceedings of Optical Fiber Communication Conference and
Exposition (OFC), 9-13 March, 2014, San Francisco (EEUU).
Extended Version to appear in Journal Of Optical Communications
and Networking January 2015
F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov,
P. Castoldi, R. Munoz, R. Martinez, "Experimenting Hierarchical
PCE Architecture in a Distributed Multi-Platform Control Plane
Testbed" , in Proceedings of Optical Fiber Communication
Conference and Exposition (OFC) and The National Fiber Optic
Engineers Conference (NFOEC), 4-8 March, 2012, Los Angeles,
California (USA).
R. Casellas, R. Martinez, R. Munoz, L. Liu, T. Tsuritani, I.
Morita, M. Tsurusawa, "Dynamic Virtual Link Mesh Topology
Aggregation in Multi-Domain Translucent WSON with Hierarchical-
PCE", in Proceedings of 37th European Conference and Exhibition on
Optical Communication (ECOC 2011), 18-22 September 2011, Geneve (
Switzerland).
R. Casellas, R. Munoz, R. Martinez, "Lab Trial of Multi-Domain
Path Computation in GMPLS Controlled WSON Using a Hierarchical
PCE", in Proceedings of OFC/NFOEC Conference (OFC2011), 10 March
2011, Los Angeles (USA).
A1.2. Telefonica Netphony (Open Source PCE)
The Telefonica Netphony PCE is an open source Java-based
implementation of a Path Computation Element, with several flavours,
and a Path Computation Client. The PCE follows a modular
architecture and allows to add customized algorithms. The PCE has
also stateful and remote initiation capabilities. In current
version, three components can be built, a domain PCE (aka child PCE),
a parent PCE (ready for the H-PCE architecture) and a PCC (path
computation client).
This work was led by:
o Oscar Gonzalez de Dios [oscar.gonzalezdedios@telefonica.com]
o Victor Lopez Alvarez [victor.lopezalvarez@telefonica.com]
o Telefonica I+D, Madrid, Spain
The PCE code is publicly available in a GitHub repository:
o https://github.com/telefonicaid/netphony-pce
The PCEP protocol encodings are located in the following repository:
o https://github.com/telefonicaid/netphony-network protocols
The traffic engineering database and a BGP-LS speaker to fill the
database is located in:
o https://github.com/telefonicaid/netphony-topology
The parent and child PCE are multi-threaded java applications. The
path computation uses the jgrapht free Java class library (0.9.1)
that provides mathematical graph-theory objects and algorithms.
Current version of netphony PCE runs on java 1.7 and 1.8, and has
been tested in GNU/Linux, Mac OS-X and Windows environments. The
management of the parent and domain PCEs is supported though CLI via
Telnet, and configured via XML files.
Further details of the netphony H-PCE prototyping and experimentation
can be found in the following research papers:
o O. Gonzalez de Dios, R. Casellas, F. Paolucci, A. Napoli, L.
Gifre, A. Dupas, E, Hugues-Salas, R. Morro, S. Belotti, G.
Meloni, T. Rahman, V.P Lopez, R. Martinez, F. Fresi, M. Bohn,
S. Yan, L. Velasco, . Layec and J. P. Fernandez-Palacios:
Experimental Demonstration of Multivendor and Multidomain EON With
Data and Control Interoperability Over a Pan-European Test Bed, in
Journal of Lightwave Technology, Dec. 2016, Vol. 34, Issue 7, pp.
1610-1617.
o O. Gonzalez de Dios, R. Casellas, R. Morro, F. Paolucci, V.
Lopez, R. Martinez, R. Munoz, R. Villalta, P. Castoldi:
"Multi-partner Demonstration of BGP-LS enabled multi-domain EON,
in Journal of Optical Communications and Networking, Dec. 2015,
Vol. 7, Issue 12, pp. B153-B162.
o F. Paolucci, O. Gonzalez de Dios, R. Casellas, S. Duhovnikov,
P. Castoldi, R. Munoz, R. Martinez, "Experimenting Hierarchical
PCE Architecture in a Distributed Multi-Platform Control Plane
Testbed" , in Proceedings of Optical Fiber Communication
Conference and Exposition (OFC) and The National Fiber Optic
Engineers Conference (NFOEC), 4-8 March, 2012, Los Angeles,
California (USA).
A1.3. H-PCE Proof of Concept developed by Huawei
Huawei developed this H-PCE on the Huawei Versatile Routing Platform
(VRP) to experiment with the hierarchy of PCE. Both end to end path
computation as well as computation for domain-sequence are supported.
This work was led by:
o Udayasree Pallee [udayasreereddy@gmail.com]
o Dhruv Dhody [dhruv.ietf@gmail.com]
o Huawei Technologies, Bangalore, India
Further work on stateful H-PCE [I-D.ietf-pce-stateful-hpce] is being Email: daniel@olddog.co.uk
carried out on ONOS.
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